10 minutes prediction should be the toughest, but at times when the market is on a stand still many guys will get the predictions right.
The 10 minute Bunny cards are also the ones which could give you the most return if you guessed correctly. But, as you said, really "predicting" the price in such a short timespan is really hard, it's more like gambling.
That's true, predictions are quite risky and for that short duration it's twice as risky. No wonder, the returns were said to be a maximum of 9703%, meaning one could make a whole lot of money from the 10 minutes volatility card.